Lens barrel and image capturing device

ABSTRACT

Provided is a lens barrel including a subject-side lens guided by guide bars, comprising a first guide shaft that is disposed within a cylindrical fixed cylinder and oriented along an axial direction of the fixed cylinder; a second guide shaft that is disposed outside the fixed cylinder and oriented along the axial direction, and arranged such that at least a portion thereof overlaps with the first guide shaft in a longitudinal direction of the first guide shaft; a first holding member that holds a first lens, includes a first engaging member that engages with the first guide shaft, and moves along the first guide shaft; and a second holding member that holds a second lens positioned on a subject side of the first lens, includes a second engaging member that engages with the second guide shaft, and moves along the second guide shaft, wherein at least a portion of movement range of the first engaging member on the first guide shaft overlaps in the axial direction with at least a portion of movement range of the second engaging member on the second guide shaft.

TECHNICAL FIELD

The present invention relates to a lens barrel and an image capturingdevice. The contents of the following Japanese patent application areincorporated herein by reference,

No. 2008-213360 filed on Aug. 21, 2008,

No. 2008-257562 filed on Oct. 2, 2008, and

No. 2009-166161 filed on Jul. 14, 2009.

BACKGROUND ART

Patent Document 1, shown below, discloses a lens barrel that includes amoving cylinder, which moves relative to a fixed cylinder while beingguided by guide pipes provided on the fixed cylinder, and a front grouplens that is guided by guide bars arranged on the moving cylinder.

Patent Document 2, shown below, discloses a lens barrel including guidebars that provide guidance in a movement direction and a lens frame thatholds a lens and has a sleeve engaging with the guide bars. A camfollower is arranged on the sleeve, and the lens frame is moved in thedirection of the optical axis of the lens according to the rotation of acam cylinder having a cam groove that engages with the cam follower.

Prior Art Documents

Patent Documents:

Patent Document 1: Japanese Patent Application Publication No.H02-210314Patent Document 2: Japanese Patent Application Publication No.H06-174998

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The lens barrels described above each have configurations in which thefront group lens moves independently relative to the guide bars.However, the rear group lens moves relative to the moving cylinder, andtherefore cannot move independently with respect to the movement of thefront group lens. Furthermore, if a plurality of lens groups that moveindependently are provided on a single guide bar, this guide bar musthave a length corresponding to the amount of movement, but a structureincluding such a guide bar results in a larger lens barrel. In aconventional lens barrel, impact from the outside can affect the camgroove and cam follower, causing damage to the cam groove or camfollower.

Means for Solving the Problems

According to a first aspect of the present invention, provided is a lensbarrel (100) comprising a first guide shaft (142) that is disposedwithin a cylindrical fixed cylinder (140) and oriented along an axialdirection of the fixed cylinder; a second guide shaft (194) that isdisposed outside the fixed cylinder and oriented along the axialdirection, and arranged such that at least a portion thereof overlapswith the first guide shaft in a longitudinal direction of the firstguide shaft; a first holding member (122) that holds a first lens (124),includes a first engaging member (161) that engages with the first guideshaft, and moves along the first guide shaft; and a second holdingmember (112) that holds a second lens (114) positioned on a subject sideof the first lens, includes a second engaging member (117) that engageswith the second guide shaft, and moves along the second guide shaft,wherein at least a portion of movement range of the first engagingmember on the first guide shaft overlaps in the axial direction with atleast a portion of movement range of the second engaging member on thesecond guide shaft.

According to a second aspect of the present invention, provided is alens barrel (100) comprising a lens holding member (212) that holds alens (211); a guide shaft (242) that guides movement of the lens holdingmember; and a cam member (250) that includes a first cam surface (251)engaging with a first cam follower (217) disposed on the lens holdingmember and a second cam surface (252) engaging with a second camfollower (219) disposed on the lens holding member, and that drives thelens holding member along the guide shaft as a result of the first camfollower engaging with the first cam surface, wherein the cam member hasa space between the second cam follower and the second cam surface.

According to a third aspect of the present invention, provided is animage capturing device (400) comprising the lens barrel (100) describedabove and an image capturing unit (300) that captures an image using thelens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the lens barrel 100.

FIG. 2 is an exploded perspective view of the lens barrel 100.

FIG. 3 is a perspective view of the fixed cylinder 240.

FIG. 4 is another perspective view of the fixed cylinder 240.

FIG. 5 is a perspective view of the intermediate unit 160.

FIG. 6 is a rear view of the intermediate unit 160.

FIG. 7 is a perspective view of the rear group unit 130.

FIG. 8 is a rear view of the rear group unit 130.

FIG. 9 is a perspective view showing movement of the intermediate unit160 and the rear group unit 130.

FIG. 10 is a perspective view showing movement of the intermediate unit160 and the rear group unit 130.

FIG. 11 is a perspective view of the cam cylinder 250.

FIG. 12 is another perspective view of the cam cylinder 250.

FIG. 13 is a perspective view of an assembly made up of the fixedcylinder 240, the intermediate unit 160, the rear group unit 130, andthe cam cylinder 250.

FIG. 14 is a perspective view of the front group unit 110.

FIG. 15 is a rear view of the front group unit 110.

FIG. 16 is a perspective view of the front group unit 110 attached tothe assembly of FIG. 13.

FIG. 17 is a cross-sectional view of the lens barrel 100.

FIG. 18 is a perspective view of an independent cam cylinder 250.

FIG. 19 is a perspective view showing a relationship between the fixedcylinder 240 and the cam cylinder 250.

FIG. 20 is a spread view of the cam cylinder 250.

FIG. 21 is a cross-sectional view schematically showing a relationshipbetween the fixed cylinder 240, the cam cylinder 250, and the slidingcylinder 216.

FIG. 22 schematically shows the configuration of the image capturingdevice 400 including the lens barrel 100.

LIST OF REFERENCE NUMERALS

-   100 lens barrel; 101 image capturing optical system; 110 front group    unit; 111 front cylinder; 112, 122, 132 lens frame; 113, 133, 163,    269, 218, 279 U-shaped groove; 114 first lens group; 116, 136, 166,    268, 278 cam follower; 117, 131, 161 engaging member; 118 screw; 119    screw hole; 121 middle cylinder; 124 second lens group; 130 rear    group unit; 134 third lens group; 135 rear cylinder; 137, 167    V-shaped groove; 138, 141, 158 notch; 139, 169 flat spring; 140, 240    fixed cylinder; 142, 144, 192, 194, 242, 261 guide bar; 143, 147,    149 bearing portion; 145 rib; 146 base; 152, 154, 156 cam groove;    150 cam cylinder; 151 zoom ring; 160 intermediate unit; 162, 264    diaphragm section; 164, 262 vibration correcting section; 170    microcomputer; 210 first group; 211 front lens; 212, 265, 275 lens    frame; 213 male lead; 214 lead ring; 216 sliding cylinder; 217    driving cam follower; 215, 267, 277 engaging portion; 219 buffering    cam follower; 220 zoom ring; 222 stopper; 241 opening; 244 mount    section; 246 cover, 250 cam cylinder; 251, 253, 254 driving cam; 252    buffering cam; 258 notch; 260 second group; 266, 276 lens; 270 third    group; 300 image capturing unit; 310 image capturing element; 312    optical filter; 320 shutter; 330 distance measuring section; 340    main mirror; 342 secondary mirror; 350 main control section; 360    mount section; 370 pentaprism; 372 focusing screen; 380 photometric    unit; 390 finder optical system; 392 half mirror; 394 finder LCD;    396 main LCD; 400 image capturing device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, some embodiments of the present invention will bedescribed. The embodiments do not limit the invention according to theclaims, and all the combinations of the features described in theembodiments are not necessarily essential to means provided by aspectsof the invention.

FIG. 1 shows a cross section of an entire lens barrel 100. The lensbarrel 100 includes an image capturing optical system 101 that containsa first lens group 114, a second lens group 124, and a third lens group134. The lens barrel 100 includes a mechanism for adjusting the focalposition, focal distance, or the like by moving at least one of the lensgroups along an optical axis of the image capturing optical system 101.The first lens group 114, the second lens group 124, and the third lensgroup 134 are respectively held by lens frames 112,122, and 132.

The fixed cylinder 140 includes a base 146 connected to other componentssuch as the camera body, and the fixed cylinder 140 does not moverelative to the camera body when the lens barrel 100 is mounted.Furthermore, the fixed cylinder 140 supports a guide bar 142 and a guidebar 144 in parallel to each other at opposite positions in the radialdirection thereof.

The fixed cylinder 140 also includes guide bars 192 and 194, forming apair. In FIG. 1, the guide bars 192 and 194 on the outside are arrangedin the same cross-sectional plane as the guide bars 142 and 144.However, this is merely meant to show that the outer guide bars 192 and194 are arranged outside the fixed cylinder 140.

The first lens group 114 is supported by the front cylinder 111 via thelens frame 112, and forms a front group unit 110 that includes the frontcylinder 111 and the lens frame 112. The front cylinder 111 is supportedtogether with the guide bars 192 and 194 as a result of an engagingmember 117 and a U-shaped groove 113 engaging with the outer guide bars192 and 194, and is driven by a cam cylinder 150 via a cam follower 116.As a result, the front group unit 110 moves relative to the fixedcylinder 140 along the optical axis of the image capturing opticalsystem 101, together with the first lens group 114. More specifically,the front group unit 110 moves toward a subject side, which is the leftside of FIG. 1, and toward an image side, which is the right side ofFIG. 1.

The second lens group 124 is supported by the middle cylinder 121 viathe lens frame 122. The middle cylinder 121 holds a diaphragm section162 and a vibration correcting section 164 to form an intermediate unit160. The vibration correcting section 164 corrects vibration, due tohand shaking or the like, by moving such that the second lens group 124has a component in a direction substantially orthogonal to the imagecapturing optical system 101.

The middle cylinder 121 moves relative to the fixed cylinder 140 alongthe optical axis of the image capturing optical system 101, as a resultof a U-shaped groove 163 of an engaging member 161 engaging with theguide bars 142 and 144, as shown in FIGS. 5 and 6. As a result, thesecond lens group 124 and the lens frame 122 held in the middle cylinder121 also move along the guide bars 142 and 144.

Concerning the longitudinal positioning of the guide bars 142, 144, 192,and 194, the guide bars 142 and 144 within the fixed cylinder 140 andthe guide bars 192 and 194 outside the fixed cylinder 140 haveoverlapping regions in which the engaging members 117 and 161 and theU-shaped grooves 113 and 163 are guided. The cam cylinder 150 isarranged between (i) the guide bars 142 and 144 and (ii) the guide bars192 and 194, and drives the front group unit 110, which is positionedradially outward, and the intermediate unit 160, which is positionedradially inward.

The third lens group 134 is held by the rear cylinder 135 via the lensframe 132. The rear cylinder 135 and the lens frame 132 form the reargroup unit 130. The rear cylinder 135 moves relative to the fixedcylinder 140 along the optical axis of the image capturing opticalsystem 101, as a result of the engaging member 131 and the U-shapedgroove 133 engaging with the guide bars 142 and 144. As a result, thethird lens group 134 and the lens frame 132 held in the rear cylinder135 also move along the guide bars 142 and 144.

The intermediate unit 160 and the rear group unit 130 are arrangedwithin the fixed cylinder 140. The front group unit 110 is arrangedoutside the fixed cylinder 140. The cam cylinder 150 can rotate on thesame rotational center as the fixed cylinder 140, according to operationof a zoom ring 151 provided on the outer circumference of the lensbarrel 100.

As described further below, the cam cylinder 150 drives the front groupunit 110, the intermediate unit 160, and the rear group unit 130 via thecam followers 116, 136, and 166. The following describes each elementindividually.

Furthermore, the lens barrel 100 houses a microcomputer 170 in additionto the above components. The microcomputer 170 performs communicationcontrol when electric signals are transmitted to or received from adevice outside the lens barrel 100.

FIG. 2 is an exploded perspective view of the lens barrel 100. The lensbarrel 100 is formed by assembling the front group unit 110, the camcylinder 150, the fixed cylinder 140, the intermediate unit 160, and therear group unit 130, in an order beginning from the left side of FIG. 2,which corresponds to the subject side, i.e. the front side.

The lens barrel 100 is assembled by sequentially performing a step ofmounting one end of each of the guide bars 142 and 144, in this case thesubject side ends, in the fixed cylinder 140 and a step of mounting theintermediate unit 160 and the rear group unit 130 from the other ends,i.e. the image side ends, of the guide bars 142 and 144. Furthermore, astep of mounting the guide bars 192 and 194 outside the fixed cylinder140 and a step of mounting the front group unit 110 on the guide bars192 and guide bar 194 are sequentially performed. These two sets ofsteps can be performed in any order. In the following description, thesubject side end of each component is referred to as the “front end.”The image side end of each component is referred to as the “back end.”

FIG. 3 is a perspective view looking down on the fixed cylinder 140diagonally from the back of the lens barrel 100. FIG. 4 is a perspectiveview looking down on the fixed cylinder 140 diagonally from the front ofthe lens barrel 100.

The fixed cylinder 140 has an overall cylindrical shape, and includesthe guide bars 142, 144, 192, and 194 and a base 146. The base 146 is aring-shaped component formed at the back end of the fixed cylinder 140,and has a mount for fixing other components to the lens barrel 100.Notches 141 are formed in the circumferential surface of the fixedcylinder 140, and the function of these notches 141 is described furtherbelow.

The pair of guide bars 142 and 144 are arranged within the fixedcylinder 140 to be parallel to the longitudinal direction of thecylinder. As shown in FIG. 3, the back ends of the guide bars 142 and144 on the image side of the lens barrel 100, i.e. the right side ofFIG. 3, are inserted through the bearing portions 147 and 149 to besupported. As shown in FIG. 4, the front ends of the guide bars 142 and144 on the subject side of the lens barrel 100, i.e. the left side ofFIG. 4, are also inserted through the bearing portions 147 and 149 to besupported. As a result, the positions of the guide bars 142 and 144 arefixed at both ends, thereby preventing skewing of the guidancedirection.

The other pair of guide bars 192 and 194 are arranged outside the fixedcylinder 140 to be parallel to the longitudinal direction of thecylinder. As shown in FIGS. 3 and 4, the back ends, i.e. image sideends, of the guide bars 192 and 194 are inserted into and supported by arib 145 formed on the outer circumference of the fixed cylinder 140 atthe approximate longitudinal center thereof. As shown in FIG. 4, thefront ends of the guide bars 142 and 144 are inserted into and supportedby a bearing portion 143 formed at the front end of the fixed cylinder.As a result, the positions of the guide bars 192 and 194 are fixed atboth ends, thereby preventing skewing of the guidance direction.

FIG. 5 is a perspective view of the intermediate unit 160. FIG. 6 is arear view of the intermediate unit 160. In FIGS. 5 and 6, a portion ofthe intermediate unit 160 is not shown.

As shown in FIG. 5, the intermediate unit 160 moves along the guide bars142 and 144 while being supported by the guide bars 142 and 144 via theengaging member 161. Since the guide bar 142 is gripped by the flatspring 169 and the V-shaped groove 167 of the engaging member 161, theintermediate unit 160 does not slip with respect to the guide bar 142.

The intermediate unit 160 includes a cam follower 166 adjacent to theengaging member 161 in the circumferential direction. As a result, theintermediate unit 160 is driven by the cam groove 154 of the camcylinder 150 as described further below. Therefore, in the imagecapturing optical system 101, the second lens group 124 can move alongthe optical axis.

As shown in FIG. 6, the middle cylinder 121 of the intermediate unit 160includes the engaging member 161 and the U-shaped groove 163. Theengaging member 161 and the U-shaped groove 163 are arrangedsymmetrically with respect to the center C in the radial direction ofthe middle cylinder 121, as shown by the dashed line A. As a result, theU-shaped groove 163 is arranged far from the engaging member 161 in theradial direction of the middle cylinder 121.

Accordingly, gaps between the U-shaped groove 163 and the guide bar 144and between the engaging member 161 and the guide bar 142 can berestricted. By accurately setting the position of the second lens group124 in a plane orthogonal to the optical axis, the center C of thesecond lens group 124 can be prevented from becoming skewed from theoptical axis of the image capturing optical system 101.

The V-shaped groove 167 of the engaging member 161 is symmetric in thecircumferential direction of the middle cylinder 121 with respect to thedashed line A. In this way, the surfaces formed by the V-shaped groove167 may be symmetric with respect to a plane including the guide bar 142and the optical axis of the image capturing optical system 101. As aresult, the combined force exerted by the surfaces of the V-shapedgroove 167 pressing on the guide bar 142 is centered toward the opticalaxis of the image capturing optical system 101, and therefore theposition of the second lens group 124 in a plane orthogonal to theoptical axis can be stabilized.

FIG. 7 is a perspective view looking down on the rear group unit 130diagonally from the front of the lens barrel 100. FIG. 8 is a rear viewof the rear group unit 130 looking from directly behind the lens barrel100.

In the rear group unit 130, the rear cylinder 135 is held within thethird lens group 134 via the lens frame 132. The engaging members 131,the cam follower 136, and the U-shaped groove 133 are formed on theouter circumferential surface of the rear cylinder 135.

The lens frame 132 and the third lens group 134 held in the lens frame132 are arranged near the back end of the rear cylinder 135, i.e. theleft side of FIG. 7. The engaging members 131 are arranged closer to thefront end of the rear cylinder 135, i.e. the right side of FIG. 7.Therefore, the third lens group 134 is arranged closer to the image sidethan the engaging member 131, with respect to the optical axis of theimage capturing optical system 101.

A notch 138 is formed on the outer circumferential surface of the rearcylinder 135 along the length thereof. A plurality of engaging members131 are formed along the circumference of the rear cylinder 135 in theregion in which the notch 138 is formed. In this way, it would appearthat a portion of the rear cylinder 135 is severed by the notch 138 tobe non-continuous in the circumferential direction, but this portion isconnected by the engaging members 131 such that the overall shape is acylinder.

As shown in FIG. 7, the engaging members 131 are arranged to bedistanced from each other in the direction in which the guide bar 142extends. As a result, symmetric slanting of the guide bar 142 and thelongitudinal direction of the rear cylinder 135 can be restricted.Furthermore, a V-shaped groove 137 is formed on the top surface of eachengaging member 131, having two contact surfaces facing each other andcontacting the guide bar 142.

When the rear group unit 130 is viewed from the rear, the cam follower136 is arranged adjacent to the engaging members 131 on the outercircumferential surface of the rear cylinder 135. The cam follower 136protrudes radially from the surface of the rear cylinder 135.

One end of the flat spring 139 is fixed to the rear cylinder 135 nearthe cam follower 136. The other end of the flat spring 139 contacts theguide bar 142. As a result, the flat spring 139 pulls the engagingmember 131 against the guide bar 142. Accordingly, the V-shaped groove137 and the guide bar 142 firmly contact each other. As a result, thecenter of the third lens group 134 is prevented from being skewed fromthe optical axis of the image capturing optical system 101.

As shown in FIG. 8, the U-shaped groove 133 engages with the guide bar144 at a different position than the engaging member 131. The U-shapedgroove 133 has a pair of contact surfaces that are parallel to eachother and that sandwich the guide bar 144 from both sides in thecircumferential direction of the rear cylinder 135. As a result,rotation of the rear cylinder 135 within a plane orthogonal to theoptical axis of the image capturing optical system 101 is restricted.

FIG. 9 shows the rear group unit 130 and the intermediate unit 160mounted in the fixed cylinder 140 and positioned on the back end side ofthe lens barrel 100. In other words, the intermediate unit 160 and therear group unit 130 are inserted into the fixed cylinder 140.

The engaging member 131 of the rear cylinder 135 engages with the guidebar 142. The cam follower 136 of the rear cylinder 135 protrudes fromthe fixed cylinder 140 via the notch 141. The engaging member 161 of theintermediate unit 160 engages with the guide bar 142, and the camfollower 166 is exposed to the outside via the notch 141 of the fixedcylinder 140.

The intermediate unit 160 and the flat springs 169 and 139 of the reargroup unit 130 are all thin, and can therefore be accommodated withinthe thickness range of the fixed cylinder 140. Accordingly, the flatsprings 169 and 139 do not protrude to the outside from the outercircumferential surface of the fixed cylinder 140.

The cam followers 166 and 136 are positioned on opposite sides of theguide bar 142 from each other in the circumferential direction of thefixed cylinder 140. Accordingly, the cam followers 166 and 136 do notinterfere with each other when they draw near each other in theextension direction of the guide bar 142.

FIG. 10 shows the rear group unit 130 and the intermediate unit 160mounted on the fixed cylinder 140 and positioned on the front end sideof the lens barrel 100. In this state as well, the cam followers 166 and136 are positioned on opposite sides of the guide bar 142 and thereforedo not interfere with each other.

in this way, the cam follower 166 of the intermediate unit 160 and thecam follower 136 of the rear group unit 130 are arranged on oppositesides of the guide bar 142 from each other, in the circumferentialdirection of the guide bar 142. Accordingly, the pair of cam followers166 and 136 do not interfere with each other even when they draw neareach other in the extension direction of the fixed cylinder 140.Therefore, the movement range of the intermediate unit 160 and the reargroup unit 130 is increased while maintaining a configuration in whichthe intermediate unit 160 and the rear group unit 130 are both guided bya single guide bar 142.

FIG. 11 is a perspective view looking down on the left surface of asingle cam cylinder 150 from behind. FIG. 12 is a perspective viewlooking down on the right side surface of the cam cylinder 150 frombehind.

The cam cylinder 150 has an overall cylindrical shape with a notch 158formed in a portion of the circumferential surface. The circumferentialsurface of the cam cylinder 150 has a plurality of cam grooves 152, 154,and 156 formed therein, which extend in both the circumferential andlongitudinal directions but do not intersect with each other.

The cam grooves 152, 154, and 156 are formed in the stated order fromthe front end side of the cam cylinder 150. In a back portion of the camcylinder 150, the cam grooves 154 and 156 are removed and the notch 158is formed. In a front portion of the cam cylinder 150, there is no notch158, and therefore the cam cylinder 150 forms a cylinder. As a result,when attached to the outer circumferential surface of the fixed cylinder140, the cam cylinder 150 rotates along the outer circumferentialsurface of the fixed cylinder 140.

FIG. 13 is a perspective view of the assembly shown in FIGS. 11 and 12with the cam cylinder 150 attached thereto. Components identical tothose in other figures are given the same reference numerals andredundant descriptions are omitted.

The cam cylinder 150 is attached to the outside of an assembly obtainedby mounting the rear group unit 130 and the intermediate unit 160 in thefixed cylinder 140. As a result, the cam followers 166 and 136protruding radially outward from the fixed cylinder 140 engage with thecam grooves 154 and 156.

After the cam cylinder 150 is attached to the outside of the fixedcylinder 140, the cam followers 136 and 166 follow the cam grooves 154and 156 from the outside of the cam cylinder 150 to be attached to therear cylinder 135 or the middle cylinder 121. At the stage shown in FIG.13, the outer guide bars 192 and 194 are exposed above the front portionof the cam cylinder 150.

The cam follower 166 of the intermediate unit 160 engages with the camgroove 154 of the cam cylinder 150. The movement direction of theintermediate unit 160 is limited to the extension direction of the guidebars 142 and 144, by the engaging member 161 and the U-shaped groove163. Accordingly, when the cam cylinder 150 rotates along the fixedcylinder 140 around the optical axis of the image capturing opticalsystem WI, the cam follower 166 is pressed by the cam groove 154 to movein the direction of the optical axis of the lens barrel 100. In thisway, the second lens group 124 held by the middle cylinder 121 movesalong the optical axis.

Similarly, the cam follower 136 of the rear group unit 130 engages withthe cam groove 156 of the cam cylinder 150. The movement direction ofthe rear group unit 130 is limited to the extension direction of theguide bars 142 and 144, by the engaging member 131 and the U-shapedgroove 133. Accordingly, when the cam cylinder 150 rotates along thefixed cylinder 140 around the optical axis of the image capturingoptical system 101, the cam follower 136 is pressed by the cam groove156 to move in the direction of the optical axis of the lens barrel 100.In this way, the third lens group 134 held by the rear group unit 130moves along the optical axis.

The cam follower 116 engages independently with the cam groove 152. Thecam follower 116 has a screw hole 119 at the center thereof. As aresult, when the front group unit 110 is attached as described below,the front cylinder 111 and the cam follower 116 can engage each other.

FIG. 14 is a perspective view of the front group unit 110. FIG. 15 is arear view of the front group unit 110. As described above, the guidebars 192 and 194 are fixed to the fixed cylinder 140, but are showntogether in FIGS. 14 and 15 to more easily show the function of thefront group unit 110.

As shown in FIG. 14, the front cylinder unit includes the front cylinder111, engaging members 117, a U-shaped groove 113, and a cam follower116. The front cylinder 111 has an overall cylindrical shape, and hasthe lens frame 112 at the front end thereof, i.e. the left side of FIG.14. The engaging members 117 and the U-shaped groove 113 are arrangednear the back end of the front cylinder 111 , i.e. the right side ofFIG. 14. As a result, the first lens group 114 is arranged closer to thesubject side than the engaging members 117 and the U-shaped groove 113in the direction of the optical axis of the image capturing opticalsystem 101.

The engaging members 117 and the U-shaped groove 113 are formed insidethe front cylinder 111 to protrude radially inward. The positions of theengaging members 117 and the U-shaped groove 113 correspond respectivelyto the positions of the pair of guide bars 192 and 194 supported by thefixed cylinder 140. Each engaging member 117 has a through-hole with adiameter through which the guide bar 194 can be smoothly inserted. As aresult, the front group unit 110 can move smoothly on the guide bars 192and 194.

The cam follower 116 is arranged near the engaging members 117 in thecircumferential direction of the front cylinder 111. When seen from theextension direction of the guide bar 194, the cam follower 116 isarranged near the center of the pair of engaging members 117. As aresult, when the cam follower 116 receives a drive force, the driveforce is evenly added to the pair of engaging members 117, and so thefront group unit 110 moves smoothly. If the front cylinder 111 is madeof resin or the like, the engaging members 117 and the U-shaped groove113 may be formed integrally.

When the front group unit 110 moves, the space between the pair ofengaging members 117 supporting the front cylinder 111 does not change.Accordingly, the form of the front cylinder 111 is stable regardless ofthe position of the front group unit 110, and changes in the opticalcharacteristics of the first lens group 114 can be prevented.

As shown in FIG. 15, the cam follower 116 protrudes inward in the radialdirection of the front cylinder 111. As a result, when the front groupunit 110 is attached to the lens barrel 100, the cam follower 116engages with the cam groove 152. Accordingly, when the earn cylinder 150rotates around the fixed cylinder 140, the cam follower 116 is pressedby the cam groove 152 to drive the entire front group unit 110.

The cam follower 116 is connected to the inside of the front cylinder111 by the screw 118. Accordingly, as shown in FIG. 13 for example, thefront group unit 110 can be mounted on the fixed cylinder 140 bymounting the front cylinder 111 after the cam follower 116 is attachedto the cam cylinder 150 and connecting the front cylinder 111 to the camfollower 116 using the screw 118.

FIG. 16 is a perspective view of the front group unit 110 mounted on theassembly shown in FIG. 13. As shown in FIG. 16, the front group unit 110is mounted on the outside of the assembly, such that the front cylinder111 encompasses the guide bars 192 and 194 from the outside. As aresult, the front group unit 110 holding the first lens group 114positioned further forward than the front end of the subject side of thefixed cylinder 140 is supported by the guide bars 192 and 194.

As described above, the cam follower 116 protruding inward in the frontcylinder 111 engages the cam groove 152 at the front end of the camcylinder 150, and so when the cam cylinder 150 rotates, the front groupunit 110 moves according to the cam profile of the cam groove 152.Accordingly, with a single operation of the cam cylinder 150, the lensbarrel 100 can perform a zoom operation with a large magnification, forexample.

The front group unit 110, the intermediate unit 160, and the rear groupunit 130 are guided on the guide bars 142 and 194 respectively by thepairs of engaging members 117, 131, and 161. Accordingly, the frontgroup unit 110, the intermediate unit 160, and the rear group unit 130each move without distorting the optical axis

FIG. 17 is a cross-sectional view of a configuration of the lens barrel100. The upper half of FIG. 17 shows a state in which the first group210 is moved back, and the lower half of FIG. 17 shows a state in whichthe first group 210 is moved forward by a zoom.

The lens barrel 100 includes a fixed cylinder 240, a cam cylinder 250, asliding cylinder 216, and a zoom ring 220 arranged coaxially on theoptical axis C. The fixed cylinder 240 includes a mount section 244 atthe back end thereot i.e. the right side of FIG. 17. The mount section244 supports the fixed cylinder 240 by engaging with a mount on a body,such as a camera.

The fixed cylinder 240 includes a pair of guide bars 242 on the outsidenear the front end thereof, i.e. the left side of FIG. 17. Both ends ofeach guide bar 242 are fixed to the fixed cylinder 240, and the guidebars 242 are parallel to the optical axis C. The cam cylinder 250 isarranged between the fixed cylinder 240 and the guide bars 242, alongthe circumferential surface of the fixed cylinder 240. The fixedcylinder 240 includes a pair of guide bars 261 on the innercircumference thereof. Both ends of each guide bar 261 are fixed to thefixed cylinder 240, and the guide bars 261 are parallel to the opticalaxis C.

The sliding cylinder 216 is arranged on the outside of the guide bars242. The sliding cylinder 216 includes an engaging portion 215 and aU-shaped groove 218 extending inward in the radial direction of the lensbarrel 100. In the example of FIG. 17, the engaging portion 215 and theU-shaped groove 218 are arranged along the guide bars 242. The engagingportion 215 and the U-shaped groove 218 each engage with a guide bar242. As a result, the sliding cylinder 216 is guided by the guide bars242 to move along a direction parallel to the optical axis C.

The sliding cylinder 216 includes a male lead 213 on the outer surfacethereof. The male lead 213 engages with a female lead on the innercircumferential surface of the lead ring 214. As a result, the lead ring214 can perform focusing by moving relative to the sliding cylinder 216.

The lead ring 214 holds the lens frame 212 therein and extends towardthe front of the guide bar 242 on the outside of the sliding cylinder216. The lens frame 212 holds a front lens 211. With this configuration,the front lens 211 moves along with the movement of the sliding cylinder216. The front lens 211 is not limited to a single lens, and may be alens group including a plurality of lenses.

The zoom ring 220 is arranged on the outside of the lead ring 214. Whenthe zoom ring 220 rotates, the cam cylinder 250 also rotates to move thesliding cylinder 216 along the guide bar, thereby integrally moving thesliding cylinder 216 to zoom together with the second group and thirdgroup described further below.

A cover 246 provides covering between the back end of the zoom ring 220and the mount section 244 of the fixed cylinder 240 in order to preventdust from entering the lens barrel 100. The cover 246 is fixed to thefixed cylinder 240 and does not rotate. The zoom ring 220 includes astopper 222 that is grasped by a user.

The lens barrel 100 further includes the second group 260 and the thirdgroup 270. The second group 260 and the third group 270 are supported byguide bars 261. The second group 260, and the third group 270 receive adrive force from the cam cylinder 250 and are guided by the guide bars261 to move in the direction of the optical axis C.

The second group 260 includes a diaphragm section 264, a lens 266, avibration correcting section 262 that corrects vibration of the lens266, and a lens frame 265 that holds the lens 266 via the vibrationcorrecting section 262. The lens frame 265 includes a pair of engagingportions 267 arranged to be distanced from each other along the guidebars 261, and a U-shaped groove 269 arranged on the opposite side of theoptical axis C from the engaging portions 267. The pair of engagingportions 267 engage with one of the guide bars 261 and the U-shapedgroove 269 engages with the other guide bar 261, thereby supporting thesecond group 260 on the guide bars 261 in a manner to allow sliding. Thelens frame 265 includes a cam follower 268 that protrudes radiallyoutward.

The third group 270 includes a lens 276 and a lens frame 275 that holdsthe lens 276. In the same manner as the lens frame 265 of the secondgroup 260, the lens frame 275 includes a pair of engaging portions 277,a U-shaped groove 279, and a cam follower 278. The configuration andoperation of the engaging portions 277 and the U-shaped groove 279 isthe same as those of the engaging portions 267 and the U-shaped groove269, and therefore further description is omitted.

FIG. 18 is a perspective view of an independent cam cylinder 250. Thecam cylinder 250 has cam grooves including driving cams 251, 253, and254 and a buffering cam 252. The driving cam 251 engages with thesliding cylinder 216 to drive the first group 210, as described furtherbelow.

In the cam cylinder 250, a region in which the driving cams 251, 253,and 254 and the buffering cam 252 are not formed is removed to form thenotch 258. As a result, the lens barrel 100 can be made lighter and thematerial used for the cam cylinder 250 can be conserved.

FIG. 19 is a perspective view showing the relationship between the fixedcylinder 240 and the cam cylinder 250. As shown in FIG. 19, the camcylinder 250 is mounted along the outer surface of the fixed cylinder240, and rotates along the circumferential surface of the fixed cylinder240.

In FIG. 19, a driving cam follower 217 and a buffering cam follower 219are inserted to the driving cam 251 and the buffering cam 252. Thesliding cylinder 216 is connected to the outer ends of the driving camfollower 217 and the buffering cam follower 219.

The driving cam 253 of the cam cylinder 250 drives the second group 260,and the driving cam 254 drives the third group 270. In accordance withthis, openings 241 are formed in the fixed cylinder 240 to allow theengaging portion 267 and cam follower 268 of the second group 260 andthe engaging portion 277 and cam follower 278 of the third group 270 tomove relative to the fixed cylinder 240.

FIG. 20 is a spread view of the earn cylinder 250. FIG. 20 also showscross sections of the driving cam follower 217 and the buffering camfollower 219 that engage with the driving cam 251 and the buffering cam252.

As shown in FIG. 20, the driving cam 251 and the buffering cam 252 havethe same shape as each other. The driving cams 253 and 254 each haveshapes that are different from the driving cam 251 and the buffering cam252.

The driving cam follower 217 engaging with the cam surface of thedriving cam 251 and the buffering cam follower 219 engageable with thecam surface of the buffering cam 252 have different radii. Specifically,the driving cam follower 217 has a radius substantially equal to thewidth of the driving cam 251. Therefore, the driving cam follower 217contacts the cam surface of the driving cam 251.

On the other hand, the buffering cam follower 219 has a radius that issmaller than the width of the buffering cam 252. Therefore, a gap isformed between the cam surface of the buffering cam 252 and thebuffering cam follower 219.

The cam follower 268 of the second group 260 is inserted into thedriving cam 253. The cam follower 278 of the third group 270 is insertedinto the driving cam 254. The width of the driving cam 253 and thediameter of the cam follower 268 are substantially the same, and thewidth of the driving cam 254 and the diameter of the cam follower 278are substantially the same. As a result, the cam follower 278 is drivenalong the driving cam 254 and the cam follower 268 is driven along thedriving cam 253 according to the rotation of the cam cylinder 250.

FIG. 21 is a cross-sectional view schematically showing a relationshipbetween the fixed cylinder 240, the cam cylinder 250, and the slidingcylinder 216. As shown in FIG. 21, the cam cylinder 250 is mounted onthe outer circumference of the fixed cylinder 240, and the slidingcylinder 216 is arranged on the outer circumference of the cam cylinder250. The guide bars 242 are between the cam cylinder 250 and the slidingcylinder 216, and are oriented to extend orthogonally from the plane ofFIG. 21. The sliding cylinder 216 includes the driving cam follower 217and the buffering cam follower 219, which protrude toward the opticalaxis of the lens barrel 100, and the engaging portion 215 and U-shapedgroove 218 that engage with the guide bars 242.

The driving cam follower 217 and the buffering cam follower 219 arerespectively inserted to the driving cam 251 and the buffering cam 252.It should be noted that although the driving cam follower 217 contactsthe cam surface of the driving cam 251, there is a gap between thebuffering cam follower 219 and the cam surface of the buffering cam 252.

The driving cam follower 217 is arranged closer to the engaging portion215 than the buffering cam follower 219 in the circumferentialdirection. As a result, the drive force received by the driving camfollower 217 can be efficiently transferred to the sliding cylinder 216.Furthermore, tilting of the front lens 211 can be restricted:

A guide bar 242 is inserted into the engaging portion 215, and the guidebar 242 is fixed to the fixed cylinder 240. Accordingly, when the camcylinder 250 rotates and the driving cam follower 217 is pressed by thedriving cam 251, the sliding cylinder 216 does not rotate.

The driving cam follower 217 contacts the cam surface of the driving cam251, and therefore the sliding cylinder 216 moves along the guide bar242 as a result of the driving cam 251 driving the driving cam follower217. Therefore, the lead ring 214, the lens frame 212, and the frontlens 211 move integrally with the sliding cylinder 216.

On the other hand, since there is a gap between the cam surface of thebuffering cam 252 and the buffering cam follower 219, the buffering camfollower 219 is not driven by the buffering cam 252. However, when anexternal mechanical load is exerted on the first group, which includesthe front lens 211, the lens frame 212, the lead ring 214, and thesliding cylinder 216, such that the driving cam follower 217 or the likeis deformed, the buffering cam follower 219 contacts the cam surface ofthe buffering cam 252 and the load is distributed. As a result, damageto the driving cam 251 and the driving cam follower 217 is prevented.

In this way, a lens barrel 100 is formed that comprises a cam cylinderincluding a lens holding unit that has a lens frame 212 holding a frontlens 211, a lead ring 214, and a sliding cylinder 216; guide bars 242that guide the movement of the lens holding unit; a driving cam 251 thatengages with a driving cam follower 217 of a sliding cylinder 216; and abuffering cam 252 that can engage with a buffering cam follower 219disposed on the sliding cylinder 216. The cam cylinder 250 drives thelens holding .unit along the guide bars 242 as a result of the drivingcam follower 217 engaging with the driving cam 251, and there is a gapbetween the buffering cam follower 219 and the buffering cam 252.

As a result, when an external load affects the first group, the load isdispersed on the buffering cam 252 and the buffering cam follower 219,thereby achieving high practical strength and increasing durability.Accordingly, the front lens 211 can be accurately guided by the guidebars 242 to prevent a decrease in the optical capabilities of the lensbarrel 100.

Considering the functions of the buffering cam follower 219 and thebuffering cam 252, the driving cam follower 217 and the buffering camfollower 219 are arranged at uniform intervals in a direction around theoptical axis C of the lens barrel 100. As a result, the load placed onthe first group 210 can be evenly distributed.

The above embodiment describes an example of a first group 210 thatfrequently experiences loads or shocks from the outside. However, if thelens barrel 100 experiences acceleration, for example, the components inthe lens barrel 100 experience the same type of shock as the firstgroup. Accordingly, by adopting the configuration of the first group 210of the above lens barrel 100, other lens groups or the like can also beprotected.

In the above embodiments, the driving cam 251 and the buffering cam 252have the same width, and a gap is formed between the buffering cam 252and the buffering cam follower 219 by changing the diameters of thedriving cam follower 217 and the buffering cam follower 219. However,the driving cam follower 217 and the buffering cam follower 219 can havethe same diameter, and the widths of the driving cam 251 and thebuffering cam 252 can be changed to form the gap between the bufferingcam 252 and the buffering cam follower 219.

Furthermore, by setting the elasticity of the buffering cam follower 219to be less than the elasticity of the driving cam follower 217, theshock dispersion effect of the buffering cam follower 219 and thebuffering cam 252 can be improved.

FIG. 22 is a schematic view of an image capturing device 400 providedwith the lens barrel 100. In order to prevent FIG. 22 from being overlycomplex, the lens barrel 100 is shown schematically. However, the lensbarrel 100 shown in FIG. 22 has the same configuration as the lensbarrel 100 described in FIG. 17. Therefore, components that are the sameas those in FIG. 17 are given the same reference numerals and redundantexplanation is omitted.

The lens barrel 100 is detachably mounted on a mount section 360 of theimage capturing unit 300. In the image capturing device 400, the lensbarrel 100 and the image capturing unit 300 are electrically connectedto each other via connection terminals, not shown. In this way, the lensbarrel 100 receives power from the image capturing unit 300.Furthermore, the lens barrel 100 may include a secondary control unitthat exchanges signals with the main control section 350 of the imagecapturing unit 300.

In the embodiment shown in FIGS. 17 to 21, the first group 210 is movedby the male lead 213 and the lead ring 214 when focusing, but thefocusing method is not limited to this, and the first group 210 may movelinearly along the guide bars 242. Furthermore, the second group 260 andthe third group 270 can be configured to include a buffering cam 252 anda buffering cam follower 219, in the same manner as the first group 210.

The image capturing unit 300 houses a main control section 350 and anoptical system that includes a main mirror 340, a pentaprism 370, and afinder optical system 390. The main mirror 340 moves between a standbyposition, in which the main mirror 340 is oriented diagonally in theoptical path of incident light through the image capturing opticalsystem 101 of the lens barrel 100, and an image capture position, whichis shown by the dotted line in FIG. 22 and in which the main mirror 340is raised out of the optical path of the incident light.

When in the standby position, the main mirror 340 guides a majority ofthe incident light to a focusing screen 372 arranged thereabove. Thefocusing screen 372 is arranged at a focal position of the imagecapturing optical system 101 of the lens barrel 100 to create an imageformed by the image capturing optical system 101.

The image created by the focusing screen 372 can be seen from the finderoptical system 390 via the pentaprism 370. Therefore, the image on thefocusing screen 372 can be seen as a normal image from the finderoptical system 390.

A half mirror 392 is arranged between the pentaprism 370 and the finderoptical system 390, and this half mirror 392 superimposes the displayimage formed by the finder LCD 394 onto the image of the focusing screen372. As a result, the image seen at the output end of the finder opticalsystem 390 is a combination of the image of the focusing screen 372 andthe image of the finder LCD 394. The finder LCD 394 displays informationconcerning image capturing conditions, setting conditions, and the likeof the image capturing device 400.

A portion of the light output from the pentaprism 370 is guided to thephotometric unit 380. The photometric unit 380 measures the intensity ofthe light and a distribution or the like thereof, and these measurementresults are referenced when determining the image capturing conditions.

The back surface of the main mirror 340, which is opposite the incidentsurface that receives the incident light, has a secondary mirror 342.The secondary mirror 342 guides a portion of the incident light passingthrough the main mirror 340 to a distance measuring section 330positioned therebelow. Therefore, when the main mirror 340 is in thestandby position, the distance measuring section 330 detects a focalpoint position that is suitable.for the subject. When the main mirror340 moves to the image capture position, the secondary mirror 342 alsomoves out of the optical path of the incident light.

A shutter 320, an optical filter 312, and an image capturing element 310are arranged on the optical axis behind the main mirror 340 relative toa direction of the incident light from the lens barrel 100. When theshutter 320 is open, the main mirror 340 moves to the image captureposition immediately therebefore, and so the incident light progressesto be incident to the image capturing element 310. As a result, theimage formed by the incident light is converted into an electric signalby the image capturing element 310.

The image capturing unit 300 is provided with a main LCD 396 facingoutward on a back surface of the lens barrel 100. The main LCD 396displays various types of setting information concerning the imagecapturing unit 300, and also displays the image formed by the imagecapturing element 310 when the main mirror 340 is in the image captureposition.

The main control section 350 performs overall control of the variousoperations described above. Furthermore, an auto-focus mechanism can beformed that drives the lens barrel 100 while referencing informationconcerning the distance to a subject as detected by the distancemeasuring section 330 of the image capturing unit 300. As anotherexample, an auto-focus mechanism can be formed by the distance measuringsection 330 referencing the movement amount of the lens barrel 100.

In this way, the image capturing device 400 can be formed to include thelens barrel 100 having the buffering cam 252 and the buffering camfollower 219. The effect of the lens barrel 100 can be realized for theimage capturing device 400 in this way. However, the use of the lensbarrel 100 is not limited to this. For example, the lens barrel 100 canbe used for a focusing mechanism, a zoom mechanism, or the like in anoptical system such as a moving image capturing mechanism, a binoculartelescope, a microscope, a surveying instrument, or the like.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

1. A lens barrel comprising: a first guide shaft that is disposed withina cylindrical fixed cylinder and oriented along an axial direction ofthe fixed cylinder; a second guide shaft that is disposed outside thefixed cylinder and oriented along the axial direction, and arranged suchthat at least a portion thereof overlaps with the first guide shaft in alongitudinal direction of the first guide shaft; a first holding memberthat holds a first lens, includes a first engaging member that engageswith the first guide shaft, and moves along the first guide shaft; and asecond holding member that holds a second lens positioned on a subjectside of the first lens, includes a second engaging member that engageswith the second guide shaft, and moves along the second guide shaft,wherein at least a portion of movement range of the first engagingmember on the first guide shaft overlaps in the axial direction with atleast a portion of movement range of the second engaging member on thesecond guide shaft.
 2. The lens barrel according to claim 1, furthercomprising a driving member that is arranged between the first guideshaft and the second guide shaft and commonly drives the first holdingmember and the second holding member.
 3. The lens barrel according toclaim 2, wherein the first holding member and the second holding membereach include a cam follower, and the driving member is a cam cylinderthat engages with the fixed cylinder and that includes cam groovesengaging with the cam followers.
 4. The lens barrel according to claim1, wherein length over which the first engaging member engages with thefirst guide shaft is constant, regardless of a position at which thefirst engaging member engages with the first guide shaft, and lengthover which the second engaging member engages with the second guideshaft is constant, regardless of a position at which the second engagingmember engages with the second guide shaft.
 5. The lens barrel accordingto claim 1, wherein the first guide shaft and the second guide shaft arefixed to the fixed cylinder at a plurality of locations on the guideshafts.
 6. The lens barrel according to claim 1, wherein at least one ofthe first guide shaft and the second guide shaft is a pair of guideshafts oriented in parallel with an axial direction orthogonal to aradial direction of the fixed cylinder.
 7. The lens barrel according toclaim 1, wherein at least one of (i) a position in the axial directionof the first lens and the first engaging member and (ii) a position inthe axial direction of the second lens and the second engaging member isskewed in the direction of the optical axis.
 8. The lens barrelaccording to claim 7, wherein the second lens is arranged further on thesubject side than the second engaging member.
 9. The lens barrelaccording to claim 7, wherein when the second lens is arranged furtheron an image side of the first lens than the second engaging member, thefirst lens is arranged further on the image side than the first engagingmember.
 10. An image capturing device comprising: the lens barrelaccording to any claim 1; and an image capturing unit that captures animage using an optical system including the first lens and the secondlens.
 11. The lens barrel according to claim 1, comprising: a lensholding member that holds a lens; a guide shaft that guides movement ofthe lens holding member; and a cam member that includes a first camsurface engaging with a first cam follower disposed on the lens holdingmember and a second cam surface engaging with a second cam followerdisposed on the lens holding member, and that drives the lens holdingmember along the guide shaft as a result of the first cam followerengaging with the first cam surface, wherein the cam member has a spacebetween the second cam follower and the second cam surface.
 12. The lensbarrel according to claim 11, wherein the lens holding member furtherincludes an engaging portion that engages with the guide shaft.
 13. Thelens barrel according to claim 12, wherein the first cam follower isarranged closer to the engaging portion than the second cam follower.14. The lens barrel according to claim 11, wherein elasticity of thefirst cam follower is higher than elasticity of the second cam follower.15. The lens barrel according to claim 11, wherein the first camfollower and the second cam follower are arranged at even intervals in adirection around an optical axis of the lens.
 16. The lens barrelaccording to claim 11, wherein the lens is a first group.
 17. The lensbarrel according to claim 11, further comprising: a second lens holdingmember that holds a second lens, which is different from the lens; and asecond guide shaft that guides movement of the second lens holdingmember.
 18. The lens barrel according to claim 17, wherein the cammember drives the second lens holding member along the second guideshaft.
 19. An image capturing device comprising: the lens barrelaccording to claim 11; and an image capturing unit that captures animage using the lens.
 20. A lens barrel comprising: a lens holdingmember that holds a lens; a guide shaft that guides movement of the lensholding member; and a cam member that includes a first cam surfaceengaging with a first cam follower disposed on the lens holding memberand a second cam surface engaging with a second cam follower disposed onthe lens holding member, and that drives the lens holding member alongthe guide shaft as a result of the first cam follower engaging with thefirst cam surface, wherein the cam member has a space between the secondcam follower and the second cam surface.